PPSS is a shell script that processess files or other items in parallel. It is
designed to make use of the current multi-core CPUs. It will detect the number
of available CPUs and start a thread for each CPU core.

This script is build with the goal to be very easy to use. Also, it must be
robust (atomic), and portable. It employs a locking mechanism and runs on
Linux and Mac OS X. It should work on other Unix-like operating system that
support the bash shell.